JP2017098206A - Secondary electrode having electrode body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery capable of suppressing generation of internal short circuit caused by a foreign substance.SOLUTION: The secondary battery solving the problem includes: an electrode body configured by laminating a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; and an internal member 200 arranged on the outside of the electrode body in a lamination direction. The internal member includes a first conductive member 110 and a second conductive member 120. The first conductive member 110 is conducted to the positive electrode or the negative electrode and the second conductive member 120 is conducted to the positive electrode or the negative electrode not conducted to the first conductive member 110, where the first conductive member 110 has an insulation coat layer 111 on a face opposed to the second conductive member 120 and the Young's modulus of the insulation coat layer 111 of the first conductive member 110 is higher than the Young's modulus of the second conductive member 120.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a secondary battery having an electrode body.

  With the development of technology and production related to mobile devices such as mobile phones and laptop computers, the demand for secondary batteries as energy sources is increasing. In particular, an increase in demand is expected in the future as a high-output power source for driving vehicles such as electric vehicles (EV), hybrid vehicles (HV), and plug-in hybrid vehicles (PHV).

  However, when the secondary battery is subjected to excessive penetration impact, such as when the battery container is crushed by an external impact, the separator between the positive and negative electrodes breaks and a short circuit occurs. There was a risk of heat generation.

  Therefore, in Patent Document 1, for example, an electrode having no active material layer (short-circuit electrode) and an insulating layer disposed between the short-circuit electrode and the outermost periphery of the electrode body are provided outside the electrode body in the battery container. A secondary battery provided has been proposed. According to this secondary battery, when a through impact is applied, heat generation is suppressed by forming a short-circuit path between the short-circuit electrode and either the positive electrode or the negative electrode closest to the outermost periphery of the electrode body. In addition, the safety of the secondary battery against penetration impact can be improved.

JP 2013-41824 A

  However, for example, when the battery components come into contact with each other due to external impact or when the battery case and the battery lid are welded, there is a possibility that conductive foreign matters such as fine metal pieces may be generated in the battery container. . In the prior art, the generated foreign matter may be mixed between the short-circuiting electrode and the insulating layer, and an internal short circuit may occur due to the mixed foreign matter penetrating the insulating layer. When an internal short circuit occurs, there is a possibility that the performance of the battery will deteriorate due to the short circuit current.

  Therefore, the present invention was created to solve the above-described conventional problems in secondary batteries, and an object thereof is to provide a secondary battery in which the occurrence of internal short circuits due to foreign substances is suppressed.

  In the secondary battery disclosed herein, an electrode body in which a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode are stacked, and an internal member disposed outside the stacking direction of the electrode body; . Here, the internal member is electrically connected to a first conductive member that is electrically connected to either the positive electrode or the negative electrode, and to a first electrode that is not electrically connected to the first conductive member. 2 conductive members. The first conductive member has an insulating coat layer on a surface facing the second conductive member, and the Young's modulus of the insulating coat layer of the first conductive member is equal to the Young's modulus of the second conductive member. It is characterized by being higher than.

  According to such a configuration, even when foreign matter is mixed between the first conductive member and the second conductive member, the second conductive member is deformed so that the foreign matter becomes the second conductive member. Since it becomes a form buried in the member, it is possible to suppress foreign matter from breaking through the insulating coat layer. That is, it is possible to suppress the occurrence of an internal short circuit due to foreign matter. Therefore, internal short circuit due to foreign matter can be suppressed, and safety against penetration impact can be improved.

It is sectional drawing which shows typically the internal structure of the secondary battery in one Embodiment of this invention from the width direction of this secondary battery. It is sectional drawing which shows typically the internal structure of the secondary battery in one Embodiment of this invention from the thickness direction of this secondary battery. It is sectional drawing which shows typically the internal structure of the secondary battery in one Embodiment of this invention from the thickness direction of this secondary battery. It is a schematic diagram which shows the whole structure of the electrode body of the secondary battery in one Embodiment of this invention. It is sectional drawing which shows typically the internal structure of the secondary battery in one Embodiment of this invention from the width direction of this secondary battery. It is the schematic diagram at the time of the foreign material mixing in the Example and comparative example of this invention.

  Hereinafter, typical embodiments of the secondary battery of the present invention will be described in detail with reference to the drawings. The embodiments described herein are, of course, not intended to limit the present invention in particular. Further, matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters for those skilled in the art based on the prior art in this field. Each drawing is schematically drawn. For example, the dimensional relationship (length, width, thickness, etc.) in each drawing does not reflect the actual dimensional relationship.

  First, the structure of the secondary battery 100 applied to this embodiment is demonstrated easily using FIG. 1 and FIG. In the present specification, the “secondary battery” refers to a battery that is charged and discharged by the movement of electric charge between the positive and negative electrodes, and a typical example includes a lithium ion secondary battery. It is not limited to the secondary battery. Moreover, in this embodiment, although the example of a wound electrode body is shown, this invention is not restricted to this, You may use a laminated electrode body.

  In the secondary battery 100 shown in FIG. 1, roughly speaking, a battery case having a flat square electrode body 20, a non-aqueous electrolyte (not shown), and an internal member (not shown) are flat and square. (That is, the outer container) 30 is accommodated. The battery case 30 has a box-shaped (that is, bottomed rectangular parallelepiped) case main body 32 having an opening at one end (corresponding to the upper end in a normal use state of the battery), and the opening of the case main body 32 is sealed. And a lid 34 to be stopped. As a material of the battery case 30, for example, a light metal material having a good thermal conductivity such as aluminum, stainless steel, or nickel-plated steel can be preferably used.

  Further, as shown in FIG. 2, the internal member includes a first conductive member 10 and a second conductive member 20 that are provided with an insulating coat layer. Here, the Young's modulus of the insulating coating layer 111 of the first conductive member 10 is higher than the Young's modulus of the second conductive member 20.

  The material of the first conductive member 10 and the second conductive member 20 is not particularly limited as long as it has conductivity, but is preferably lightweight and has good thermal conductivity such as aluminum, stainless steel, and nickel-plated steel. Metal materials can be preferably used. The material of the insulating coating layer applied to the first conductive member 10 is not particularly limited as long as the Young's modulus is higher than that of the second conductive member 20 and the insulating property is high, but silica glass or acrylic glass is not limited. Amorphous solids such as natural rubber and synthetic rubber, polyphenylene sulfide (PPS) as an engineering plastic, and perfluoroalkoxy fluororesin (PFA) as a fluorinated resin copolymer. Synthetic resins and the like can be used.

  Here, the first conductive member 10 is electrically connected to the negative electrode 60, and the second conductive member 20 is electrically connected to the positive electrode 50. In the description of the present embodiment and in FIG. 2, the first conductive member 10 is described so as to be closer to the electrode body than the second conductive member 20. As long as the insulating coating layer of one conductive member 10 faces the second conductive member 20, the positional relationship between the first conductive member 10 and the second conductive member 20 may be switched.

  Further, as shown in FIG. 3, either the first conductive member 10 or the second conductive member 20 may be a battery case 30. When either the first conductive member 10 or the second conductive member 20 is the battery case 30, it is not necessary to newly prepare either the first conductive member 10 or the second conductive member 20. Since the electrode body can be filled in the battery container by the thickness of the conductive member or the second conductive member, it is possible to obtain a secondary battery with higher energy density.

  Further, as shown in FIG. 1, the lid 34 is set to release the internal pressure when the internal pressure of the battery case 30 rises above a predetermined level, and the positive terminal 42 and the negative terminal 44 for external connection. A thin safety valve 36 and an injection port (not shown) for injecting a non-aqueous electrolyte are provided. The battery case 30 may be provided with a current interruption device (CID) that operates when the internal pressure of the battery case 30 increases.

  As shown in FIGS. 1 and 4, the electrode body 20 disclosed herein has a positive electrode active material layer 54 along the longitudinal direction on one side or both sides (here, both sides) of an elongated positive electrode current collector foil 52. The formed positive electrode 50 and the negative electrode 60 in which the negative electrode active material layer 64 is formed on one side or both sides (here, both sides) of the long negative electrode current collector foil 62 along the longitudinal direction. The laminated body laminated | stacked through the separator 70 of a shape is wound by the elongate direction, and has the form shape | molded by the flat shape.

  As shown in FIG. 1 and FIG. 4, the wound core portion (that is, the positive electrode active material layer 54 of the positive electrode 50, the negative electrode active material layer 64 of the negative electrode 60, and the central portion of the electrode body 20 in the winding axis direction) , A laminated structure in which separators 70 are laminated). In addition, at both ends of the electrode body 20 in the winding axis direction, a part of the positive electrode active material layer non-formed part 52a and a part of the negative electrode active material layer non-formed part 62a protrude outward from the wound core part. The positive electrode side protruding portion (positive electrode active material layer non-forming portion 52a) and the negative electrode side protruding portion (negative electrode active material layer non-forming portion 62a) are respectively provided with a positive electrode current collecting plate 42a and a negative electrode current collecting plate 44a. The terminal 42 and the negative terminal 44 are electrically connected to each other.

Examples of the positive electrode current collector foil 52 constituting the positive electrode 50 include an aluminum foil. The positive electrode active material layer 54 contains at least a positive electrode active material. Examples of the positive electrode active material include lithium composite metal oxides such as a layered structure and a spinel structure (for example, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiFePO _4, etc.). The positive electrode active material layer 54 may include components other than the active material, for example, a conductive material such as carbon black such as acetylene black (AB), a binder such as polyvinylidene fluoride (PVDF), and the like.

  Examples of the negative electrode current collector foil 62 constituting the negative electrode 60 include copper foil. The negative electrode active material layer 64 contains, for example, a carbon material such as graphite or hard carbon as the negative electrode active material. The negative electrode active material layer 64 may include components other than the active material, for example, a binder such as styrene butadiene rubber (SBR), a thickener such as carboxymethyl cellulose (CMC), and the like.

  Such a positive electrode 50 and a negative electrode 60 can be produced as follows, for example. First, a positive electrode active material or a negative electrode active material and a material used as necessary are combined with an appropriate solvent (for example, an organic solvent such as N-methyl-2-pyrrolidone for a positive electrode active material, or ion exchange for a negative electrode active material A paste-like (slurry) composition is prepared by dispersing in an aqueous solvent such as water. Next, the composition can be formed by applying an appropriate amount of the composition to the surface of the positive electrode current collector foil 52 or the negative electrode current collector foil 62 and then removing the solvent by drying. Moreover, the properties (for example, average thickness, active material density, porosity, etc.) of the positive electrode active material layer 54 and the negative electrode active material layer 64 can be adjusted by performing an appropriate press treatment as necessary.

  Examples of the separator 70 include a porous sheet (film) made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. Such a porous sheet may have a single layer structure or a laminated structure of two or more layers. A heat resistant layer (HRL) may be provided on the surface of the separator 70.

As the nonaqueous electrolytic solution, typically, an organic solvent (nonaqueous solvent) containing a supporting salt can be used. As the non-aqueous solvent, organic solvents such as various carbonates, ethers, esters, nitriles, sulfones and the like used for an electrolyte solution of a general lithium ion secondary battery can be used without particular limitation. As the supporting salt, for example, a lithium salt such as LiPF ₆ , LiBF ₄ , or LiClO ₄ can be suitably used.

  The non-aqueous electrolyte includes components other than the non-aqueous solvent and the supporting salt described above, for example, a gas generating agent such as biphenyl (BP) and cyclohexylbenzene (CHB); an oxalato complex containing a boron atom and / or a phosphorus atom. Various additives such as a compound, a film forming agent such as vinylene carbonate (VC), fluoroethylene carbonate (FEC); a dispersant; a thickener;

  EXAMPLES Examples (test examples) relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples (test examples).

The electrode bodies according to the first example 1 and the second example were constructed by the following materials and processes.
<First embodiment>
The positive electrode was produced by the following procedure. LiNi _0.33 Co _0.33 Mn _0.33 O ₂ (LNCM) as a positive electrode active material powder, AB as a conductive material, and PVDF as a binder, LNCM: AB: PVDF = 90: 8: 2 A slurry-like composition for forming a positive electrode active material layer was prepared by mixing with NMP at a mass ratio of The composition was applied to both sides of a 15 μm-thick long aluminum foil (positive electrode current collector foil) in a strip shape, dried and pressed to prepare a positive electrode sheet. The coating amount of the positive electrode active material layer forming composition and the pressing conditions were adjusted so that the average thickness of the positive electrode was about 65 μm (the average thickness per one side of the positive electrode active material layer was about 25 μm).

  The negative electrode was produced according to the following procedure. First, graphite (C) whose surface was coated with amorphous carbon was prepared as a negative electrode active material powder. And this graphite (C), SBR as a binder, and CMC as a thickener are mixed with ion exchange water at a mass ratio of C: SBR: CMC = 98: 1: 1, A composition for forming a negative electrode active material layer was prepared. This composition was applied to both sides of a long copper foil (negative electrode current collector foil) having a thickness of 10 μm in a strip shape, dried, and pressed to prepare a negative electrode sheet. The amount of the negative electrode active material layer-forming composition applied and the pressing conditions were adjusted so that the average thickness of the negative electrode was about 80 μm (the average thickness per one side of the negative electrode active material layer was about 35 μm).

  In the positive electrode and negative electrode produced as described above, a porous polypropylene layer was formed on both sides of the porous polyethylene layer, and a layer made of alumina particles and a binder (so-called heat resistant layer) was formed on the surface of one of the polypropylene layers. The sheets were overlapped in the longitudinal direction via two separators having a four-layer structure, and wound up (wound) 60 times in the longitudinal direction (that is, the number of times of winding). Then, the electrode body (the positive electrode, the negative electrode, and the separator after winding) was crushed in one direction perpendicular to the winding axis, and a flat electrode body was produced.

  Next, as an internal member, a silica glass coat (insulating coat layer) having a thickness of 50 μm and a Young's modulus of 94 GPa is applied to a copper foil (first conductive member 10) having a thickness of 10 μm and a Young's modulus of 124 GPa. An aluminum foil (second conductive member 20) having a thickness of 15 μm and a Young's modulus of 69 GPa was stacked so as to face the coat layer, and was cut out at a length of one or more circumferences of the outer periphery of the electrode body. In this embodiment, the length of the inner member is set to be equal to or longer than one circumference of the outer periphery of the electrode body, but the surface of the electrode body orthogonal to the direction in which the electrode body is crushed (or the stacking direction of the electrode bodies). This is not necessarily the case as long as it can cover the size.

  Next, the internal members stacked in this order of the first conductive member 10 and the second conductive member 20 are arranged outside the electrode body 20 in the stacking direction as shown in FIG. Then, the negative electrode 60 of the electrode body and the first conductive member 10 were fixed so that the positive electrode 50 of the electrode body and the second conductive member 20 were electrically connected to each other. In this embodiment, as an electrical connection method, the negative electrode 60 and the first conductive member 10 are fixed by the connection member 112 of the first conductive member as shown in FIG. 5, and the positive electrode 50 and the second conductive member are fixed. Although it fixes by making it weld by the connection member 121 of a 2nd electrically-conductive member, this invention is not limited to the fixing method, A current collection terminal by a conductive adhesive, resistance welding, ultrasonic welding, etc. It may be fixed to. Moreover, you may connect a electrically-conductive member and a current collection terminal directly, without using a connection member. The connection member 112 of the first conductive member and the connection member 121 of the second conductive member are not particularly limited as long as they are conductive materials, and this time, aluminum foil was used.

A positive electrode lead terminal and a negative electrode lead terminal were respectively attached to the non-formed part of the positive electrode active material layer and the non-formed part of the negative electrode active material layer of the electrode body by ultrasonic welding means. Thereafter, the electrode body and the internal member were accommodated in a box-shaped battery container together with the non-aqueous electrolyte, and the opening of the battery container was hermetically sealed. As the non-aqueous electrolyte, 41 g of a non-aqueous electrolyte in which LiPF6 as a supporting salt was contained at a concentration of about 1 mol / liter in a mixed solvent containing EC, DMC, and EMC in a volume ratio of 3: 4: 3 was used. . The sealed prismatic lithium ion secondary battery thus constructed was subjected to an initial charge / discharge treatment (conditioning) by a conventional method to produce a secondary battery.
<First comparative example>
Since the battery of the first comparative example has the same configuration as that of the first embodiment except that the configuration of the internal members is different, the overlapping description is omitted.

In the first comparative example, the internal member is made by stacking a PP coat (insulating member) with a thickness of 50 μm on an aluminum foil (first conductive member 10) instead of a silica glass coat (insulating coat layer) with a thickness of 50 μm. It is a thing. Note that the Young's modulus of the first conductive member 10 in this comparative example is 124 GPa, the Young's modulus of the PP coat is 1 GPa, and the Young's modulus of the second conductive member 20 is 69 GPa. Other materials, configurations, and manufacturing methods are the same as those in the first embodiment.
<Second Comparative Example>
Since the battery of the second comparative example has the same configuration as that of the first embodiment except that the configuration of the internal members is different, the overlapping description is omitted.

  In the second comparative example, the internal member is made of a 50 μm thick aluminum foil (first conductive member 10) applied with a 50 μm thick silica glass coat (insulating coat layer), and a 10 μm thick copper foil (second conductive member). The conductive member 20) is overlaid. The Young's modulus of the first conductive member 10 in this comparative example is 69 GPa, the Young's modulus of the silica glass coat is 94 GPa, and the Young's modulus of the second conductive member 20 is 124 GPa. Other materials, configurations, and manufacturing methods are the same as those in the first embodiment.

  Next, counting from the inner layer direction of the electrode body, the internal members laminated in the order of the first conductive member 10 and the second conductive member 20 are arranged outside the electrode body in the lamination direction, and the negative electrode of the electrode body and the second The two conductive members 20 were fixed so as to be electrically connected to each other. In this embodiment, as an electrical connection method, the positive electrode and the first conductive member are connected to the first conductive member using the connection member 112, and the negative electrode and the second conductive member are connected to the second conductive member. Although it fixes by making it weld each using 121, this invention is not limited to the fixing method, You may fix using other methods, such as using a conductive adhesive.

Moreover, it fixed with the insulating member of the internal member fixed to the electrode body, and the battery case in contact. In this embodiment, fixing is performed using an adhesive, but the fixing method is not limited thereto.
<Forced internal short circuit test>
In order to investigate the effect of the battery of the present invention, a forced internal short-circuit test was performed on the secondary batteries of Examples and Comparative Examples. In addition, the test method was performed based on the "forced internal short circuit test" of JISC8714. However, regarding the position of the nickel piece, the experiment was performed by installing it between the first conductive member and the second conductive member. The results are shown in Table 1.

  As shown in Table 1, when the Young's modulus of the insulating coating layer of the first conductive member 10 as in Example 1 is higher than the Young's modulus of the second conductive member 20, it was confirmed that an internal short circuit can be suppressed. .

  Here, with reference to FIG. 6, a mechanism that can suppress the internal short circuit in the first embodiment will be described. FIG. 6 is a schematic diagram when foreign matter is mixed in the example of the present invention and the comparative example.

  In FIG. 6A, in Comparative Example 1, the foreign matter mixed between the first conductive member 10 and the second conductive member 20 is the first conductive member as the electrode body expands as the battery is charged / discharged. 10 insulating coat layers and the second conductive member 20. At this time, since the Young's modulus of the insulating coating layer of the first conductive member 10 is equal to or lower than the Young's modulus of the second conductive member 20, the foreign matter is equal to the second conductive member 20 or the first conductive member 10. It is easy to be buried in the insulating coating layer. That is, there is a possibility that foreign matter penetrates the insulating coat layer, and the first conductive member 10 and the second conductive member 20 are energized by the foreign matter. Therefore, when a foreign substance is mixed between the first conductive member 10 and the second conductive member 20, a short circuit due to the foreign substance has occurred.

  On the other hand, in the embodiment shown in FIG. 6B, the foreign matter mixed between the first conductive member 10 and the second conductive member 20 is caused by the expansion of the electrode body accompanying the charging / discharging of the battery. It is pressed against the insulating coat layer of the conductive member 10 and the second conductive member 20. At this time, since the Young's modulus of the insulating coating layer of the first conductive member 10 is larger than the Young's modulus of the second conductive member 20, the foreign matter is not the insulating coating layer of the first conductive member 10, but the second conductive material. It is buried in the member 20. Therefore, even when foreign matter does not penetrate the insulating coat layer and foreign matter is mixed between the first conductive member 10 and the second conductive member 20, occurrence of a short circuit due to the foreign matter can be suppressed.

  Here, the Young's modulus of the insulating coating layer is preferably 1.3 times or more, more preferably 1.36 times or more, compared to the Young's modulus of the second conductive member. According to such a configuration, occurrence of a short circuit due to a foreign substance can be suppressed with higher accuracy.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

  Moreover, in the said Example, although the square battery which has metal packages was employ | adopted, it is not restricted to this form. For example, a square battery or a cylindrical battery having a metal package, a battery having a laminate film package, or a battery having a synthetic resin package may be used.

  In the battery of the above embodiment, the power generation region and the exposed region of the positive electrode sheet are both made of aluminum, but both need not be made of aluminum. When applied to a general lithium secondary battery, aluminum excellent in stability at a high potential is preferable.

  In the negative electrode sheet, both the power generation area and the exposed area are made of copper, but both need not be made of copper. These metal foils constituting the electrodes can be used without particular limitation as long as they are conductive metals. For example, metal materials such as aluminum, copper, titanium, nickel, iron, and stainless steel can be used.

  The technical elements described in the present specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings achieves a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

  The technical elements described in the present specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings achieves a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

DESCRIPTION OF SYMBOLS 20 Electrode body 30 Battery case 32 Battery case main body 34 Lid body 36 Safety valve 42 Positive electrode terminal 42a Positive electrode current collecting plate 44 Negative electrode terminal 44a Negative electrode current collecting plate 50 Positive electrode 52 Positive electrode current collector 52a Positive electrode active material layer non-formation part 54 Positive electrode active material Layer 60 Negative electrode 62 Negative electrode current collector 62a Negative electrode active material layer non-formed portion 64 Negative electrode active material layer 70 Separator 100 Secondary battery 110 First conductive member 111 Insulation coating layer 112 of first conductive member First conductive member Connection member 120 Second conductive member 121 Connection member 130 of second conductive member Foreign matter 200 Internal member

Claims (1)

An electrode body in which a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode are stacked, and an internal member disposed outside in the stacking direction of the electrode body,
The internal member includes a first conductive member and a second conductive member,
The first conductive member is electrically connected to either the positive electrode or the negative electrode, and the second conductive member is electrically connected to either the positive electrode or the negative electrode that is not electrically connected to the first conductive member. A secondary battery,
The first conductive member has an insulating coat layer on a surface facing the second conductive member,
A secondary battery, wherein the Young's modulus of the insulating coating layer of the first conductive member is higher than the Young's modulus of the second conductive member.